Generally, an ampoule 1 as shown in FIG. 1 has a head portion 2 whose top end 3 is opened before charging a liquid agent in the ampoule. After the liquid agent has been charged in the ampoule through the opening, the top end 3 is heated to close the opening by fusing. The thus fused head portion 2 normally has, as shown in FIG. 2, a cavity which gradually enlarges by having a smaller upper diameter a1 than a lower diameter b1, but the entire head portion has a glass wall of a thickness w1 which is substantially uniform. In external appearance, the top end 3 contours a smoothly curved surface and merges into a lower wall contouring a smoothly inclined surface.
However, depending on conditions of a burner flame used for fusing, there result various types of defective products. In an example shown in FIG. 3A. a head portion has a cavity which has a larger upper diameter a2 than a lower diameter b2 and a non-uniform glass wall as defined by different thicknesses w2 and w3 where w2&lt;w3, and an external appearance specified by an expanded top end 3'. In another example as shown in FIG. 3B, a top end 3' is flattened. Conversely, in still another example as shown in FIG. 3C, a top end 3' is sharpened. In a head portion as exemplified in FIG. 3D, a top end 3' droops.
The ampoule 1 having the top end 3 shown in FIG. 2 faces no problem of quality insurance and besides, has an excellent external appearance, thus being handled as a good product which does not disturb normal use. However, when taking the product of FIG. 3A among the defective products of FIGS. 3A to 3D, for instance, this product is liable to breakage because of a thin wall region of the thickness w2, having difficulties with quality insurance and is degraded in external appearance. Therefore, this defective product should be put in disposal. For checking whether the thickness and the external form of products are acceptable or not, a standard is set up.
Ampoules with fused head portions must be examined one by one as to whether they have thicknesses or external forms which conform to the standard, in order to detect defective products. Conventionally, to this end, an inspector holds by hand each ampoule in front of a white board and light is irradiated on the ampoule in order for the inspector to check with the eye an image projecting on the white board.
This checking method has been valid for detecting a product with a largely deformed head portion but disadvantageously, has almost been invalid for detecting a small deformation and consequently failed to accurately detect defective ampoules. In addition, detection efficiency of this method has been very poor.